To prevent a crack from occurring on a sheared end face due to press forming, a technology is provided for evaluating and predicting a crack limit of the sheared end face of a metal sheet and determining press forming conditions. In a deformation limit evaluation method for, when deforming by press forming a metal sheet subjected to shearing, evaluating a deformation limit of the sheared end face of the metal sheet, the deformation limit is evaluated by an index value obtained from two stress gradients at an evaluation position among stress distributions occurring in the vicinity of the sheared end face of the metal sheet due to the press forming, which gradients are a stress gradient in a sheet thickness direction and a stress gradient in a direction away from the sheared end face.
Legal claims defining the scope of protection, as filed with the USPTO.
3. The method of claim 1, wherein the index value is defined as a root mean square of the gradients of the two surface stress distributions.
4. The method of claim 1, wherein the index value is defined as a sum of the gradients of the two surface stress distributions.
7. The method of claim 5, wherein the press die shape of the manufactured press die has a bending radius that is larger than a test bending radius at which the deformation limit strain εlimit was measured by the two or more tests.
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August 2, 2018
February 28, 2023
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